Utilization of pre-operative MRI to identify AIS patients at highest risk of intra-operative neuromonitoring alert.

PURPOSE: Utility of pre-operative MRI for patients undergoing scoliosis correction has expanded to include an MRI classification for identifying patients at increased risk of experiencing intra-operative neuromonitoring (IONM) alerts based on the shape of the spinal cord and circumferential presence of CSF at the apex of the thoracic curve. In the present study, the authors explore the utility of this new MRI classification and multiple X-ray radiographic parameters in identifying the AIS sub-population at high risk of IONM alerts.

METHODS

AIS patients < 18 years old who underwent posterior spinal fusion between 2018 and 2022 at a single institution. Imaging reviewed to determine main thoracic (MT) and thoraco-lumbar (TL) Cobb angles, major thoracic Apical Vertebral Translation (AVT) and lumbar/thoraco-lumbar AVT (TL AVT), thoracic kyphosis (TK), coronal main thoracic Deformity Angular Ratio (cDAR), sagittal DAR (sDAR), and MRI to determine the spinal cord type (1, 2, or 3).

RESULTS

A total of 155 AIS patients who met the inclusion criteria between 2018 and 2022 were included. There was a trend to have an increased incidence of Type 3 spinal cord shape both with increase in the MT Cobb angle and MT AVT. There was also a shift toward more IONM alerts in patients with Type 3 (19.5%) spinal cords, AVT ≥ 5 cm (18.9%), and Cobb angle ≥ 650 (28.2%).

CONCLUSION

Higher magnitude of thoracic Cobb angle and AVT are associated with higher likelihood of type 3 spinal cord at the apex in MRI. Patients with Type 3 spinal cord, Cobb angle ≥ 650, AVT > 5 cm, and cDAR > 10 have higher likelihood to have IONM alerts. Patient with a Type 3 spinal cord and a Cobb angle ≥ 650 (50.0%), cDAR > 10 (43.7%), and AVT > 5 cm (35.2%) have the highest risk of having IONM alerts.